Confusion with default domain!

Hi Folks

Brand new here so hope you'll be gentle!

I've set up the ZCS (latest v 7.x) on a CentOS 6.2 server and all seems to be OK. I've set up the primary domain as serverhostname.ourdomain.com but the server is handling multiple domains, one of which is ourdomain.com.

Here's the issue. If I set up a domain ourdomain.com as an alias to the primary domain (serverhostname.ourdomain.com) then no matter if I log in as me@ourdomain.com, the outgoing message has a sender of:

I'm now wondering if I should have set the ZCS up with ourdomain.com as the primary, with the servername.ourdomain.com as the alias. I know that someone is going to say "but why do you need the alias?" - it's because this will be the third mailserver with the same domain as default and we use a virtusertable on our main server to split them all up. So depending on which server the customer is located, we send to server 1 or server 2 or this server and the account for this primary domain on all servers is set up with ourdomain.com as the primary and serverhostname.ourdomain.com as the alias.

If you answer YES to the question "Should I change the default primary to ourdomain.com and make servername.ourdomain.com the alias?" to YES, then could someone please tell me if there is a way to do this without having to blow the domains all away and add them again? I have a number of users already added so would prefer to be able to simply swap the two domains around if possible.

Sure. I manually copied all the mailboxes in the default domain to a secondary domain I created, then deleted the default domain. The default domain from setup was the server FQDN, which wasn't the domain I wanted as default. Then I recreated the server FQDN as an alias to the "new" default domain. It works a treat.